Neurodevelopmental outcomes after neonatal cardiac surgery: Role of cortical isoelectric activity

Objectives: Neonates with congenital heart disease are at risk for impaired neurodevelopment after cardiac surgery. We hypothesized that intraoperative EEG activity may provide insight into future neurodevelopmental outcomes. Methods: Neonates requiring surgery had continuous intraoperative EEG and hemodynamic monitoring. The level of EEG suppression was classified as either: slow and continuous; moderate burst suppression; severe burst suppression; or isoelectric (no brain activity for > 3 minutes). Follow-up neurodevelopmental outcomes were assessed using the Vineland Adaptive Behavior Scale II (Vineland-II). Results: Twenty-one neonates requiring cardiac surgery developed a slow and continuous EEG pattern after general anesthesia. Ten neonates (48%) maintained continuous brain electrical activity with moderate burst suppression as the maximum level of EEG suppression. Eleven neonates (52%) developed severe burst suppression that progressed into an isoelectric state during the deep hypothermic period required for circulatory arrest. However, the duration of this state was significantly longer than circulatory arrest times (111.1 +/- 50 vs 22.3 +/- 17 minutes; P < .001). At a mean follow-up at 5.6 +/- 1.0 years, compared with neonates with continuous brain electrical activity, neonates who developed an isoelectric state had lower Vineland-II scores in communication. There was an inverse relationship between composite Vineland-II scores and duration of isoelectric activity (R = -0.75, P = .01). Of neonates who experienced an isoelectric state, durations of >90 minutes were associated with the lowest Vineland-II scores (125.0 +/- 2.6 vs 81.1 +/- 12.7; P < .01). Conclusions: The duration of cortical isoelectric states seems related to neurodevelopmental outcomes. Strategies using continuous EEG monitoring to minimize isoelectric states may be useful during complex congenital heart surgery.